Critical heat capacity in a 3-methylpentane + nitroethane mixture near its consolute point

A computerized high-resolution ac calorimetric technique has been used to measure the heat capacity $C_{\mathrm{px}}$ of a critical 3-methylpentane + nitroethane binary-liquid mixture. An analysis of these results yields universal parameters in good agreement with those expected for the $d=3\mathrm{}$, $n=1\mathrm{}$ (three-dimensional Ising) universality class. The critical exponent $\alpha ={\alpha }^{\prime }$ lies in the range 0.11-0.12, the ratio $\frac{A^{\prime }}{A}$ of the amplitudes of the leading singularity in $C_{\mathrm{px}}$ above and below $T_c$ is 1.79±0.06. The ratio of the corrections-to-scaling amplitudes $\frac{D^{\prime }}{D}$ is ∼1. The quantity $\frac{A_v{\xi }_0^3}{k_B}$, which relates the critical amplitude of the heat capacity to that of the correlation length, is also in agreement with the renormalization-group value for the three-dimensional Ising model as expected from two-scale-factor universality.